This invention relates to delivering data optically to an integrated circuit.
In integrated circuit (IC) design there are areas of concern for designers: IC density and size, IC power dissipation, and IC speed. The IC, containing many millions of sub-micron transistors, has become more dense and smaller in size. The power dissipation per square area has increased but it is reduced when the IC is powered with a low voltage. A metal trace provides DC voltages and electronic digital data to an integrated circuit at a maximum data rate at about 500 MHz.
In general, in one aspect, the invention is directed to a system including a multi-sided module having a cavity housing a substrate, n photoreceivers located on a side of the substrate and adapted to receive a beam of collimated light directed by a waveguide and an integrated circuit (IC) positioned at the substrate to receive output from the photoreceiver.
This aspect may include one or more of the following features. The system has a beam of collimated light that includes a first laser light packet. The laser light packet includes a first set of n laser light pulses. The beam of collimated light comes from a network. The n photoreceivers are connected to a first set of n transistors and include n photodetectors for converting the first set of n laser light pulses to a first set of n electronic pulses and n receivers for converting the first set of n electronic pulses to a first digitized packet. The system also includes a first set of n latches for storing the digitized packet, and a first set of n buffers for amplifying and delivering the first digitized packet from the first set of n latches to the IC. In addition, the system includes a second set of n transistors activated by a clock pulse, the second set of n transistors transferring the first digitized packet to the first set of n latches. The system includes a second set of k latches for storing a second digitized packet sent by the IC, where kxe2x89xa71, the second digitized packet having a second set of k electronic pulses, and a second set of k buffers for amplifying and delivering the second set of k electronic pulses to a multiplexer.
The system also includes a laser controller for receiving a series of k electronic pulses from the multiplexer and a laser light source receiving an input from the laser controller and sending a second laser packet having a second set of k light pulses to the network. The system may have k=n, where nxe2x89xa71. The substrate includes a first surface and a second surface opposite to the first surface, the first surface is in contact with the module and the sides of the substrate and the second surface are not in contact with the module. The beam of collimated light is injected horizontally into the substrate. Multiple wavelengths are injected into the substrate at once.
In general, in another aspect, the invention is directed to a method that directs a beam of collimated light through a waveguide positioned at a multi-sided module towards n photoreceivers located at a side of a substrate contained in a cavity of the module; and sends an output of the n photoreceivers to an integrated circuit.
Embodiments of the invention may have one or more of the following advantages. The system provides optical data to an integrated circuit at 1 GHZ and beyond. By having the photodetectors on the sides of the substrate, design improvements can be made at the module at a greater cost savings than the more costly design changes at the substrate that can be an IC chip. The high yield of the IC chip remains intact since the aggressive processes are directed to the module. Since the photodetector is part of the substrate, there is no need for additional layers and masks or other special manufacturing processes.
Lateral injection of laser light to the IC chip is possible which improves the frequency and the dynamic range of the photodetector. In the proposed configuration, the photodetector becomes extremely sensitive to laser light of energy in the aJ (atto Joule) range.
Multi-wavelengths of laser light can be used simultaneously to increase significantly the data transmission rate.